Past research has found significant relations among parental knowledge about adolescents' activities, peer alcohol use, and later alcohol use disorders (AUDs). However, these relations must be considered in the context of genetic risk. That is, an adolescent's genetic risk for disinhibited behavior may affect both the amount of knowledge that caregivers have about the adolescent's life, the adolescent's choice of peer group, and the adolescent's likelihood of developing alcohol problems. However, the effects of parental knowledge and peer influences over and above genetic risk are not well-understood. Few studies have tested parental knowledge and peer influences over and above genetic risk scores that explain substantial variance in the outcomes. Past research also suggests that the effect of environment may vary according to level of genetic risk, but no study to date has examined the relations among parental knowledge, peer alcohol use, and offspring alcohol problems at different levels of a broad genetic risk score. The proposed study will address these questions using data taken from an ongoing longitudinal study of familial alcoholism spanning three generations. I will create broad genetic risk scores that may explain larger proportions of the variance in emerging/young adult alcohol use problems by utilizing several genetic variants (e.g. DRD2, DAT1, GABRA1, and OPRM1). The study will examine the influences of parental knowledge and peer alcohol use over and above gene-environment covariation (i.e., the relations between adolescent genetic risk and parental knowledge, and adolescent genetic risk and peer alcohol use) and will determine whether the relations among parental knowledge, peer alcohol use, and alcohol problems are stronger for adolescents at particular levels of genetic risk (i.e. gene-environment interaction). The proposed study provides an excellent opportunity to better understand the relative influences of parental knowledge, peer alcohol use, and genetic risk on emerging/young adult alcohol use problems and to draw implications for the prevention of underage drinking. PUBLIC HEALTH RELEVANCE: The proposed research has important public health implications, because of the high prevalence of alcohol disorders and their associated costs. It is important to understand the unique effects of parental knowledge and peer alcohol use over and above correlated genetic risk and the extent to which these influences interact with genetic risk to predict alcohol use problems. A better understanding of the unique effects of parental knowledge and peer influence on alcohol use problems, and their interaction with genetic risk will inform prevention and intervention programs aimed at decreasing risk for such problems.